So I've been crossing the US MX border every month to visit MX for less than a day or for the weekend for years. The MX border by land never checks anything, I've never been asked to show my ID when I cross into mexico.
How does the Mexican immigration know when I have left the country (I mean they know when I cross back to the USA since they check my Green Card) if I for example, overstayed? And viceversa, how does the US immigration know how long I have been gone for? I'm guessing they just assume I was there for a day or two since I have a job and everything in the US and pay taxes but if they want to be so strict about giving a US citizenship to immigrants, shouldn't they enforce or check who is leaving the country even by land? I'm guessing in Canada they do check when you leave to Canada.